Michaela J. ConleyMarion McElweeLiyana AzmiMads GabrielsenOlwyn ByronIan G. GoodfellowDavid Bhella2024-05-282024-05-28201918/2/20200028-08362409-110.1038/s41586-018-0852-1https://www.nature.com/articles/s41586-018-0852-1https://oarep.usim.edu.my/handle/123456789/4341Conley, M.J., McElwee, M., Azmi, L. et al. Calicivirus VP2 forms a portal-like assembly following receptor engagement. Nature 565, 377–381 (2019). https://doi.org/10.1038/s41586-018-0852-1To initiate infection, many viruses enter their host cells by triggering endocytosis following receptor engagement. However, the mechanisms by which non-enveloped viruses escape the endosome are poorly understood. Here we present near-atomic-resolution cryo-electron microscopy structures for feline calicivirus both undecorated and labelled with a soluble fragment of its cellular receptor, feline junctional adhesion molecule A. We show that VP2, a minor capsid protein encoded by all caliciviruses1,2, forms a large portal-like assembly at a unique three-fold axis of symmetry, following receptor engagement. This assembly—which was not detected in undecorated virions—is formed of twelve copies of VP2, arranged with their hydrophobic N termini pointing away from the virion surface. Local rearrangement at the portal site leads to the opening of a pore in the capsid shell. We hypothesize that the portal-like assembly functions as a channel for the delivery of the calicivirus genome, through the endosomal membrane, into the cytoplasm of a host cell, thereby initiating infection. VP2 was previously known to be critical for the production of infectious virus3; our findings provide insights into its structure and function that advance our understanding of the Caliciviridae.enCryoelectron microscopySAXSVirus–host interactionsVirus structuresArticle3773815657739